Topical anesthetics are widely used agents that are absorbed by the skin and temporarily block nerve endings that perceive inflammation and other skin injury. The active agent is generally incorporated in an oil-based carrier comprising a lotion or liquid that is poured and spread over the skin in a thin layer or sprayed thereon using a pump or pressurized aerosol formulation. Many topical aesthetic agents are known, perhaps the most widely used being lidocaine, prilocaine, xylocaine, benzocaine and the like. These may be combined with one another in a form of dual relief action or also combined with other agents such a antihistamines, anti-inflammatory agents or antiseptic compositions for multiple action relief.
U.S. Pat. No. 5,013,545 to Blackmon et. al. discloses and claims aqueous gel-containing topical medications comprising high concentrations of alcohol, water and topically effective amounts of a pharmaceutical active such as hydrocortisone, diphenhydramine hydrochloride, lidocaine or miconazale nitrate in a gel matrix primarily consisting of water-soluble carboxyvinyl polymers. A gel clarifying agent may be optionally added for aesthetic reasons.
U.S. Pat. No. 4,937,078 to Mezie et. al. discloses the incorporation of similar topical anesthetic actives into liposomes which essentially encapsulate the active with layers of lipid material. It is asserted that the lipid vesicles provide a more pronounced cutaneous anesthetic or analgesic effect while employing less of the topical anesthetic agent. The lipid vesicles allegedly provide a means of controlling the permeation rate without the risk for discomfort due to numbness or systemic reactions.
U.S. Pat. No. 5,081,158 to Pomerantz discloses the use of medicated protective films as a carrier for topical anesthetics. The films are comprised of hydroxypropyl cellulose (HPC) and an esterification agent which renders the HPC soluble in a non-volatile solvent such as ethanol, isopropanol or methanol. Medicinal compounds such as benzocaine, dyclonine hydrochloride and a variety of other topical anesthetics, antibiotics and steroids are incorporated which, when applied to the skin, result in situ formed medicated films from which the actives are released to provide a sustained supply of the medicine at the treatment site.
U.S. Pat. No. 5,002,974 to Geria discloses a topical anesthetic and skin moisturizing composition comprising any one of a number of topical anesthetics, including pramoxine, in an oil-in-water emulsion including a dissolved surface active agent. The composition is asserted to provide an aesthetically pleasing analgesic skin care product. The emulsion not only provides relief from the pain associated with irritated skin but is asserted to soften and moisturize the skin with an oily coating.
Finally, U.S. Pat. No. 4,493,591 to Fourman et al discloses skin care cosmetic formulations comprised of a cellulosic polymer/solvent system capable of dispersing thin, substantive films upon the skin. Such films may serve as a carrier for sun blocking agents and insect repellents and also serve to prevent water loss form the skin surface to the environment. U.S. Pat. No. 4,389,418 to Burton et. al., in a more general and traditional sense, discloses the use of hydrocarbons such as petrolatum, paraffin wax and ozokerite and other emollients as skin moisturizing materials. These function by covering the skin with a hydrophobic occlusive film which prevents water loss from the skin to the environment.
While the foregoing topical anesthetics and moisturizers possess valuable pain-killing and skin softening properties when utilized in creams and lotions, they are also generally regarded as aesthetically undesirable in that they lack good tactile properties, are visible when worn and generate a greasy, oily feel.